I would say, hiragana and katakana, in a way.

Each nominal syllable sound in Japanese can be written using a characater in one of these two scripts:

Roman transcription: a i u e o ka ki ku ke ko

Hiragana: あ い う え お か き く け こ

Katakana: ア イ ウ エ オ カ キ ク ケ コ

There are some rough parallels between upper case and katakana.

- Katakana is used less than hiragana; "katakana heavy" text will be something that is loaded with foreign words (like a software manual) or terms from zoology and botany.

- It is sometimes used to denote SHOUTING, like in quoted speech such as cartoon bubbles.

- Some early computing displays in the west could only produce upper case characters; in Japan, some early displays only featured katakana. It needs less resolution for clarity.